1. Field of the Invention
The present invention relates to a powder transport screw for transporting a toner and other such powder, and a development device, process unit and image-forming apparatus comprising this powder transporting screw.
Furthermore, a spiral direction reversal part of this transport screw is constituted by connecting together blade parts that spiral in opposite directions from one another, and a V-shaped groove is formed at the connection portion of the blade part and the blade part. When toner enters into this V-shaped groove, it can be hard for the toner to detach from this groove. Then, when toner that has entered inside the V-shaped groove deteriorates, the fluidity of this toner decreases, and the toner clumps together inside the groove. The build up of toner resulting from the clumped toner causes problems, such as a reduction in the transporting function of the transport screw, and the clogging of the transport route.
Further, this clumping and accumulation of the toner inside the groove can also occur in the spiral direction reversal part, which carries the toner out toward both ends of the transport screw in the axial direction, but is more apt to occur in the spiral direction reversal part that carries the toner in from both ends of the transport screw due to the toner density becoming higher.
2. Description of the Related Art
A copier, printer, facsimile machine or an image-forming apparatus that is a composite of these, for example, comprises a transport screw like that shown in Japanese Patent Application Laid-open No. 2003-107828 as transporting means for transporting a toner. A portion, where the direction of the spiral of this helical blade reverses, is disposed part way along this transport screw. Rotating this transport screw in one direction transports the toner from the portion where the direction of the spiral is reversed (hereinafter referred to as the spiral direction reversal part) toward both ends of the transport screw in the axial direction. Further, rotating this transport screw in the opposite direction makes it possible to transport toner from both ends of the transport screw in the axial direction toward the spiral direction reversal part.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent No. 3,851,530.